Compression/multi-screen process of digital video signals may be used in a digital video recorder (DVR) which converts analog images into digital images and records/stores such images, or displays such images real time.
Ordinarily, a DVR must compress and record multi-channel video signals inputted from a number of cameras, and must display such signals on multi-screens.
Among various modules constituting such DVR system, the compression unit and the multi-screen processor are the most important modules. In the conventional multi-channel DVR systems, such compression units and multi-screen processors are set apart as independent modules.
The multi-thread scaling means to process screens of different resolutions alternating the even field and the odd field of interlacing.
FIG. 1 is a diagram illustrating a conventional DVR system with an independent compression unit and an independent multi-screen processor.
Operations of the compression unit (10) illustrated in FIG. 1 are explained herein below. First of all, the central processing unit (“CPU”) (13) initializes the analog/digital converters (11), and the compression FIFO (12) in the pre-determined order. Such initialized analog/digital converters (11) store digital data in the compression FIFO (12) and issues to the CPU (13) an interrupt exception handling request. Although the CPU (13) may fetch video data after polling the analog/digital converters (11), the compression FIFO (12) is used in order to decrease the load on the CPU (13), to increase the video data transmission efficiency, and to reduce transmission errors. The CPU (13)'s exception handling routine transmits video data from the compression FIFO (12) to the memory (RAM) (30) by a direct memory access method, encodes such data using compression algorithms such as MPEG, JPEG, and H.26x, etc., and then stores the data in a storage such as a hard disk.
The multi-screen processor (20) as illustrated in FIG. 1 operates as follows. In the multi-screen processor, the video processor (23) transmits digitalized video data from the multi-screen FIFO (22) to the video memory (31) according to the pre-determined rules set for the multi-screen processing. Then, such data are processed to constitute multi-screens, such as 4/8/16 screens, on a TV or a VGA monitor.
As explained above, the conventional system has independent modules for the compression unit (10) and the multi-screen processor (20) because the compression unit (10) and the multi-screen processor (20) are programmed to process video data in different resolutions. In other words, the compression unit (10) may process video data real time only if it is programmed to be a 30 frame transmission mode at the resolution of 352×240. Also, the multi-screen processor (2) for 16 screens, for example, may process video data real time only if it is programmed to bc a 30 frame transmission mode at the resolution of 180×120. Therefore, the conventional N-channel real time DVR with independent compression unit (10) and multi-screen processor (20) requires 2×N analog/digital converters.
However, ordinary analog/digital converters consume an extraordinary amount of the current, which causes great consumption of electric power. Accordingly, they generate a significant amount of heat impairing stability of the system. Furthermore, conventional multi-channel DVR systems are expensive because (N channel)×2 analog/digital converters are required.